Organic light-emitting diode and method of fabricating the same

ABSTRACT

An organic light-emitting diode includes an anode on a substrate; a first hole transporting layer on the anode; a second hole transporting layer on the first hole transporting layer and corresponding to the red and green pixel areas; a first emitting material pattern of a first thickness on the second hole transporting layer and corresponding to the red pixel area; a second emitting material pattern of a second thickness on the second hole transporting layer and corresponding to the green pixel area; a third emitting material pattern of a third thickness on the first hole transporting layer and corresponding to the blue pixel area; an electron transporting layer on the first, second and third emitting material patterns; and a cathode on the electron transporting layer, wherein the second thickness is less than the first thickness and greater than the third thickness.

The present application claims the priority benefit of Korean PatentApplication No. 10-2012-0092979 filed in Republic of Korea on Aug. 24,2012, which is hereby incorporated by reference.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates to an organic light-emitting diode, andmore particularly, to an organic light-emitting diode capable ofreducing the number of masks required in a fabrication process tothereby reduce a fabricating cost and simplify the fabrication process,and a method of fabricating the organic light-emitting diode.

2. Discussion of the Related Art

A cathode ray tube (CRT) has been used as a display for variouselectronics for a long time. However, recently, flat panel displaydevices, such as a plasma display panel (PDP), a liquid crystal display(LCD), and an organic light-emitting diode (OLED) display device, havebeen developed and widely used.

Among the above-mentioned flat panel display devices, the organiclight-emitting diode display device can be fabricated as a lightweight,slim display since it is a self-luminous device requiring no backlight.

Also, the organic light-emitting diode display device has lowconsumption power, allows direct-current low-voltage driving, has a highresponse speed, is highly resistant to external impacts since theinternal element is solid, and also has a wide operating temperaturerange.

Particularly, since the organic light-emitting diode display device canbe fabricated with a simple fabrication process, it can be fabricatedwith a lower fabrication cost than a liquid crystal display device.

FIG. 1 is a circuit diagram showing the structure of a pixel of aconventional active matrix type organic light-emitting diode displaydevice.

Referring to FIG. 1, a pixel of the active matrix type organiclight-emitting diode display device includes a switching thin filmtransistor STr, a driving thin film transistor DTr, a storage capacitorStgC, and an organic light-emitting diode E.

Also, gate lines GL are formed in a first direction, data lines DL areformed in a second direction crossing the first direction, and a powerline PL for supplying a voltage is formed to be spaced apart from a dataline DL.

The switching thin film transistor STr is formed at a crossing of a dataline DL and a gate line GL, and electrically connected to the drivingthin film transistor DTr.

The driving thin film transistor DTr is electrically connected to theorganic light-emitting diode E. That is, a first electrode of theorganic light-emitting diode E corresponding to one terminal of theorganic light-emitting diode E is connected to the drain electrode ofthe drain thin film transistor DTr, and a second electrode of theorganic light-emitting diode E corresponding to the other terminal ofthe organic light-emitting diode E is connected to the ground. The powerline PL transfers a supply voltage to the organic light-emitting diodeE. Also, the storage capacitor StgC is formed between the gate electrodeand source electrode of the driving thin film transistor DTr.

Accordingly, if a signal is applied through the gate line GL, theswitching thin film transistor STr is turned on, a signal of the dataline DL is transferred to the gate electrode of the driving thin filmtransistor DTr to turn on the driving thin film transistor DTr, so thatlight is emitted through the organic light-emitting diode E. If thedriving thin film transistor DTr is turned on, a level of currentflowing from the power line PL to the organic light-emitting diode E isdecided so that the organic light-emitting diode E can implement a grayscale. Also, the storage capacitor StgC acts to maintain the gatevoltage of the driving thin film transistor DTr constant when theswitching thin film transistor STr is turned off, to thereby maintainthe level of the current flowing through the organic thin film diode Econstant until a next frame even when the switching thin film transistorSTr is turned off.

As shown in FIG. 2, the organic light emitting diode E includes an anode10 on which red, green, and blue pixel areas Rp, Gp, and Bp are defined,a hole transporting layer 12, an emitting material layer consisting of ared organic light-emitting pattern 14, a green organic light-emittingpattern 16, and a blue organic light-emitting pattern 18, an electrontransporting layer 20, and a cathode 22. Although not shown in FIG. 2, ahole injection layer may be disposed between the anode 10 and the holetransporting layer 12, and an electron injection layer may be disposedbetween the cathode 22 and the electron transporting layer 20

In the organic light-emitting diode E, if voltages are applied to theanode 10 and the cathode 22, holes and electrons are transferred to theemitting material layer, and coupled with each other in the emittingmaterial layer to thereby emit light. However, the conventional organiclight-emitting diode has limitations in light output efficiency andcolor properties.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an organiclight-emitting diode display device that substantially obviates one ormore of the problems due to limitations and disadvantages of the relatedart.

An object of the present disclosure is to provide an organiclight-emitting diode display device with improved light outputefficiency and color properties.

Another object of the present disclosure is to provide a method offabricating an organic light-emitting diode display device, capable ofimproving light output efficiency without an additional mask process forpreventing a fabrication cost from increasing and a fabrication processfrom being complicated.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided an organic light-emitting diode including: a substrateon which a red pixel area, a green pixel area, and a blue pixel area aredefined; an anode disposed on the substrate and corresponding to the redpixel area, the green pixel area, and the blue pixel area; a first holetransporting layer disposed on the anode and corresponding to the redpixel area, the green pixel area, and the blue pixel area; a second holetransporting layer disposed on the first hole transporting layer andcorresponding to the red pixel area and the green pixel area, the secondhole transporting layer having a uniform thickness; a first emittingmaterial pattern disposed on the second hole transporting layer andcorresponding to the red pixel area, the first emitting material patternhaving a first thickness; a second emitting material pattern disposed onthe second hole transporting layer and corresponding to the green pixelarea, the second emitting material pattern having a second thickness; athird emitting material pattern disposed on the first hole transportinglayer and corresponding to the blue pixel area, the third emittingmaterial pattern having a third thickness; an electron transportinglayer disposed on the first emitting material pattern, the secondemitting material pattern, and the third emitting material pattern andcorresponding to the red pixel area, the green pixel area, and the bluepixel area; and a cathode disposed on the electron transporting layerand corresponding to the red pixel area, the green pixel area, and theblue pixel area, wherein the second thickness is less than the firstthickness and greater than the third thickness.

In another aspect, there is provided a method of fabricating an organiclight-emitting diode, including: forming an anode on the entire surfaceof a substrate on which a red pixel area, a green pixel area, and a bluepixel area are defined; forming a first hole transporting layer on theanode and corresponding to the red pixel area, the green pixel area, andthe blue pixel area; forming a second hole transporting layer on thefirst hole transporting layer and corresponding to the red pixel areaand the green pixel area, the second hole transporting layer having auniform thickness; forming a red organic light-emitting pattern on thesecond hole transporting layer and corresponding to the red pixel area;forming a green organic light-emitting pattern on the red organiclight-emitting pattern and the second hole transporting layer; forming ablue organic light-emitting pattern on the green organic light-emittingpattern and the first hole transporting layer; forming an electrontransporting layer on the blue organic light-emitting pattern; andforming a cathode on the electron transporting layer.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a circuit diagram showing the structure of a pixel of aconventional active matrix type organic light-emitting diode displaydevice;

FIG. 2 is a cross-sectional view of a conventional organiclight-emitting diode;

FIG. 3 is a cross-sectional view of an organic light-emitting diodeaccording to a first embodiment of the present invention;

FIG. 4 is a cross-sectional view of an organic light-emitting diodeaccording to a second embodiment of the present invention;

FIGS. 5A and 5B are graphs showing emission spectrums of red and greenpixel areas in the organic light-emitting diodes according to theembodiments of the present invention; and

FIGS. 6A and 6B are graphs showing emission spectrums of organiclight-emitting diodes in which different lamination structures areapplied to red and green pixel areas.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments,examples of which are illustrated in the accompanying drawings.

FIG. 3 is a cross-sectional view of an organic light-emitting diodeaccording to a first embodiment of the present invention.

As shown in FIG. 3, the organic light-emitting diode includes an anode110 applied on a substrate (not shown) on which red, green, and bluepixel areas Rp, Gp, and Bp are defined, a hole injection layer 120, afirst hole transporting layer 122, a second hole transporting layer 124,a third hole transporting layer 126, an electron blocking layer 130, anemitting material layer consisting of a red organic light-emittingpattern 142, a green organic light-emitting pattern 144, and a blueorganic light-emitting pattern 146, an electron transporting layer 150,a cathode 160, and a capping layer 170.

Also, although not shown in FIG. 3, in an organic light-emitting diodedisplay device including the organic light-emitting diode, a power lineis disposed to extend parallel to one of gate lines and data lines thatcross each other on the substrate to define the pixel areas Rp, Gp, andBp, and each of the pixel areas Rp, Gp, and Bp includes a switching thinfilm transistor connected to a gate line and a data line, and a drivingthin film transistor connected to the switching thin film transistor.The driving thin film transistor is connected to the anode 110.

The hole injection layer 120, the first hole transporting layer 122, thesecond hole transporting layer 124, the third hole transporting layer126, the electron blocking layer 130, the red organic light-emittingpattern 142, the green organic light-emitting pattern 144, the blueorganic light-emitting pattern 146, and the electron transporting layer150 configure an organic light-emitting layer.

The anode 110 is formed in the shape of a plate in the red, green, andblue pixel areas Rp, Gp, and Bp, and the other components areindependently formed in the respective red, green, and blue pixel areasRp, Gp, and Bp. The anode 110 is a reflective electrode, and may includea transparent, conductive material layer formed of a material having ahigh work function, such as indium-tin-oxide (ITO), and a reflectivematerial layer formed of a material such as Ag or an Ag alloy.

The hole injection layer 120 and the first hole transporting layer 122are disposed on the anode 110, in correspondence to all the red, green,and blue pixel areas Rp, Gp, and Bp. The first hole transporting layer122 is a common hole transporting layer, and the hole injection layer120 may be omitted. The total thickness of the hole injection layer 120and the first hole transporting layer 122 may be about 1250 Å, but maybe adjusted in consideration of the characteristics of hole injectionand hole transportation.

The second and third hole transporting layers 124 and 126 are disposedon the first hole transporting layer 122, in correspondence to the redand green pixel areas Rp and Gp. The second hole transporting layer 124is thicker than the third hole transporting layer 126. The second holetransporting layer 124 may have a thickness of about 750 Å, and thethird hole transporting layer 126 may have a thickness of about 500 Å.However, the thicknesses of the second and third hole transportinglayers 124 and 126 may be adjusted as long as the second holetransporting layer 124 is thicker than the third hole transporting layer126.

The electron blocking layer 130 is disposed on the second and third holetransporting layers 124 and 126 and the first hole transporting layer122 corresponding to the blue pixel area Bp. The electron blocking layer130 causes electrons emitted from the cathode 160 to stay in theemitting material layer. The electron blocking layer 130 may be omitted.

The red organic light-emitting pattern 142, the green organiclight-emitting pattern 144, and the blue organic light-emitting pattern146 are positioned in correspondence to the red, green, and blue pixelareas Rp, Gp, and Bp, respectively, and the red organic light-emittingpattern 142 is thicker than the green and blue organic light-emittingpatterns 144 and 146. The red organic light-emitting pattern 142 has athickness of about 400 Å, and each of the green and blue organiclight-emitting patterns 144 and 146 has a thickness of about 200 Å.However, the thicknesses of the red, green, and blue organiclight-emitting patterns 142, 144, and 146 may be adjusted as long as thered organic light-emitting pattern 142 is thicker than the green andblue organic light-emitting patterns 144 and 146.

The electron transporting layers 150 are disposed on the red, green, andblue organic light-emitting patterns 142, 144, and 146. Each electrontransporting layer 150 has a thickness of about 350 Å, however, thethickness of the electron transporting layer 150 may be adjusted inconsideration of the characteristics of electron transportation. Theelectron transporting layer 150 may function as an electron transportingand injection layer, and an electron injection layer may be formed onthe electron transporting layer 150.

The cathode 160 is positioned on the electron transporting layer 150.For example, the cathode 160 is formed of an alloy (Mg:Ag) of magnesium(Mg) and silver (Ag) to have a semi-transparent property. That is, lightemitted from the emitting material layer is displayed to the outsidethrough the cathode 160, and a part of the light returns to the anode110 since the cathode 160 has the semi-transparent property.

As such, repeated reflection occurs between the anode 110 acting as areflective layer and the cathode 160, which is called a microcavityeffect. That is, since light is repeatedly reflected in the cavitybetween the anode 110 and the cathode 160, light efficiency increases.

At this time, since light emitted from the respective red, green, andblue organic light-emitting patterns 142, 144, and 146 has differentwavelengths, the thickness of a cavity defined as the distance betweenthe anode 110 and the cathode 160 is differentiated. That is, in the redpixel area Rp from which red light having a longest wavelength isemitted, the anode 110 and the cathode 160 are spaced a first distanced1 apart, in the blue pixel area Bp from which blue light having ashortest wavelength is emitted, the anode 110 and the cathode 160 arespaced a third distance d3 apart, and in the green pixel area Gp fromwhich green light is emitted, a second distance d2 between the anode 110and the cathode 160 is shorter than the first distance d1 and longerthan the third distance d3 (d1>d2>d3).

Accordingly, the first hole transporting layer 122 is formed on theentire surface of the red, green, and blue pixel areas Rp, Gp, and Bp,the second hole transporting layer 124 is additionally formed on the redpixel area Rp, and the third hole transporting layer 126 that is thinnerthan the second hole transporting layer 124 is formed on the green pixelarea GP.

Meanwhile, the capping layer 170 is used to enhance a light extractioneffect, and may be formed of one among materials for forming the first,second, third hole transporting layers 122, 124, and 126, materials forforming the electron transporting layer 150, and host materials forforming the red, green, and blue organic light-emitting patterns 142,144, and 146. However, the capping layer 170 may be omitted.

As such, the organic light-emitting diode having the microcavitystructure has improved light emitting efficiency and color properties,however, each of the pixel areas Rp, Gp, and Bp requires an additionalmask process to differentiate the thickness of cavity.

In order to differentiate the thickness of cavity between the pixelareas Rp, Gp, and Bp, there is a method of forming the red organiclight-emitting material pattern 142 with a very thick thickness.However, a light-emitting material pattern that is too thick causesdeterioration of emitting efficiency, which negates the effect of themicrocavity structure.

Accordingly, by making the second hole transporting layer 124 formed inthe red pixel area Rp thicker than the third hole transporting layer 126formed in the green pixel area Gp, no separate hole transporting layeris formed in the blue pixel area Bp.

Meanwhile, fine metal masks having openings in correspondence to thepixel areas Rp, Bp, and B are used to form material patterns in therespective pixel areas Rp, Bp, and Gp. Accordingly, in order to form thesecond and third hole transporting layers 124 and 126 having differentthicknesses, it is necessary to perform processes using fine metal masksin different chambers.

Referring again to FIG. 3, after the anode 110 is formed, the holeinjection layer 120 and the first hole transporting layer 122 are formedusing a first fine metal mask. The hole injection layer 120 is formed bydoping a material for forming the first hole transporting layer 122 witha p-type dopant, for example, boron, and the hole injection layer 120and the first hole transporting layer 122 may be formed using the firstfine metal mask in a first chamber.

Then, in a second chamber, the second hole transporting layer 124 isformed in the red pixel area RP using a second fine metal mask, and in athird chamber, the third hole transporting layer 126 is formed in thegreen pixel area Gp using a third fine metal mask.

Successively, in a fourth chamber, the electron blocking layer 130 isformed in the red, green, and blue pixel areas Rp, Gp, and Bp using afourth fine metal mask, and in fifth, sixth, and seventh chambers, thered, green, and blue organic light-emitting patterns 142, 144, and 146are formed using fifth, sixth, and seventh fine metal masks.

Thereafter, in eighth, ninth, and tenth chambers, the electrontransporting layer 150, the cathode 160, and the capping layer 170 aresequentially formed using eighth, ninth, and tenth fine metal masks.

That is, in order to implement the microcavity structure, processes haveto be performed using 10 fine metal masks in a total of 10 chambers,which leads to an increase of a fabrication cost, and complexity of afabrication method.

Hereinafter, an organic light-emitting diode capable of overcoming thisproblem will be described with reference to FIG. 4, which is across-sectional view of an organic light-emitting diode according to asecond embodiment of the present invention.

As shown in FIG. 4, the organic light-emitting diode includes an anode210, a hole injection layer 220, a first hole transporting layer 222, asecond hole transporting layer 224, an electron blocking layer 230, anemitting material layer consisting of a red organic light-emittingpattern 242, a green organic light-emitting pattern 244, and a blueorganic light-emitting pattern 246, an electron transporting layer 250,a cathode 260, and a capping layer 270 stacked on a substrate (notshown) on which red, green, and blue pixel areas Rp, Gp, and Bp aredefined.

Although not shown in FIG. 4, in an organic light-emitting diode displaydevice including the organic light-emitting diode, a power line isdisposed to extend parallel to one of gate lines and data lines thatcross each other on the substrate to define the pixel areas Rp, Gp, andBp, and each of the pixel areas Rp, Gp, and Bp includes a switching thinfilm transistor connected to a gate line and a data line, and a drivingthin film transistor connected to the switching thin film transistor.The driving thin film transistor is connected to the anode 210.

The hole injection layer 220, the first hole transporting layer 222, thesecond hole transporting layer 224, the electron blocking layer 230, thered organic light-emitting pattern 242, the green organic light-emittingpattern 244, the blue organic light-emitting pattern 246, and theelectron transporting layer 250 configure an organic light-emittinglayer. That is, the organic light-emitting diode includes the anode 210and the cathode 260 that face each other, and the organic light-emittinglayer interposed between the anode 210 and the cathode 260.

The anode 210 is formed in the shape of a plate in the red, green, andblue pixel areas Rp, Gp, and Bp, and the other components areindependently formed on the respective red, green, and blue pixel areasRp, Gp, and Bp. The anode 210 is a reflective electrode, and may includea transparent, conductive material layer formed of a material having ahigh work function, such as indium-tin-oxide (ITO), and a reflectivematerial layer formed of a material, such as Ag or an Ag alloy.

The hole injection layer 220 and the first hole transporting layer 222are disposed on the anode 210, in correspondence to all of the red,green, and blue pixel areas Rp, Gp, and Bp. The first hole transportinglayer 222 is a common hole transporting layer, and the hole injectionlayer 220 may be omitted. The total thickness of the hole injectionlayer 220 and the first hole transporting layer 222 may be about 1250 Å,but may be adjusted in consideration of the characteristics of holeinjection and hole transportation.

The second hole transporting layer 224 is positioned on the first holetransporting layer 222, in correspondence to the red and green pixelareas Rp and Gp.

That is, in the first embodiment shown in FIG. 3, the second and thirdhole transporting layers 124 and 126 having different thicknesses arerespectively formed in the red and green pixel areas RP and Gp, whereasin the second embodiment, the second hole transporting layer 224 havinga uniform thickness is formed in the red and green pixel areas Rp andGp. Meanwhile, like the first embodiment, in the second embodiment, noseparate hole transporting layer is formed in the blue pixel area Bp.

The electron blocking layer 230 is formed on the second holetransporting layer 224 of the red and green pixel areas Rp and Gp andthe first hole transporting layer 222 of the blue pixel area Bp. Theelectron blocking layer 230 causes electrons emitted from the cathodes260 to stay in the emitting material layer. However, the electronblocking layer 230 may be omitted.

The red organic light-emitting pattern 242 is disposed in the red pixelarea Rp, the green organic light-emitting pattern 244 is disposed in thered and green pixel areas Rp and Gp, and the blue organic light-emittingpattern 246 is formed in all of the red, green, and blue pixel areas Rp,Gp, and Bp. The red organic light-emitting pattern 242 may be thickerthan the green and blue organic light-emitting patterns 244 and 246. Thered organic light-emitting pattern 242 has a thickness of about 450 Å,and each of the green and blue organic light-emitting patterns 244 and246 has a thickness of about 200 Å. However, the thicknesses of the red,green, and blue emission patterns 242, 244, and 246 may be adjusted aslong as the red organic light-emitting pattern 242 is thicker than thegreen and blue organic light-emitting patterns 244 and 246.

That is, in the red pixel area Rp, the red organic light-emittingpattern 242, the green organic light-emitting pattern 244, and the blueorganic light-emitting pattern 246 are stacked to form a first emittingmaterial pattern 247 with a three-layered structure, in the green pixelarea Gp, the green organic light-emitting pattern 244 and the blueorganic light-emitting pattern 246 are stacked to form a second emittingmaterial pattern 248 with a two-layered structure, and in the blue pixelarea Bp, the blue organic light-emitting pattern 246 forms a thirdemitting material pattern 249 with a signal layer. Accordingly, thesecond emitting material pattern 248 is thinner than the first emittingmaterial pattern 247 and thicker than the third emitting materialpattern 249.

The electron transporting layer 250 is formed on the blue organiclight-emitting patterns 246 formed in the red, green, and blue pixelareas Rp, Gp, and Bp. The electron transporting layer 250 has athickness of about 350 Å, however, the thickness of the electrodetransporting layer 250 may be adjusted in consideration of thecharacteristics of electron transportation. The electron transportinglayer 250 acts as a layer for electron transportation and injection, oran electron injection layer may be formed on the electron transportinglayer 250.

The cathode 260 is disposed on the electron transporting layer 150. Forexample, the cathode 260 is formed of an alloy (Mg:Ag) of magnesium (Mg)and silver (Ag) to have a semi-transparent property. That is, lightemitted from the emitting material layer is displayed to the outsidethrough the cathode 260, and a part of the light returns to the anode210 since the cathode 260 has the semi-transparent property.

As such, repeated reflection occurs between the anode 210 acting as areflective layer and the cathode 260, which is called a microcavityeffect. That is, since light is repeatedly reflected in the cavitybetween the anode 210 and the cathode 260, light efficiency increases.

At this time, since light emitted from the first, second, and thirdemitting material patterns 247, 248, and 249 formed respectively in thered, green, and blue pixel areas Rp, Gp, and Bp has differentwavelengths, the thickness of a cavity defined as the distances betweenthe anode 210 and the cathode 260 is differentiated. That is, in the redpixel area Rp from which red light having a longest wavelength isemitted, the anode 210 and the cathode 260 are spaced a first distanced1 apart, in the blue pixel area Bp from which blue light having ashortest wavelength is emitted, the anode 210 and the cathode 260 arespaced a third distance d3 apart, and in the green pixel area Gp fromwhich green light is emitted, a second distance d2 between the anode 210and the cathode 260 is shorter than the first distance d1 and longerthan the third distance d3 (d1>d2>d3).

In order to obtain the difference in thickness, after the first holetransporting layer 222 is formed on the entire surface of the red,green, and blue pixel areas Rp, Gp, and Bp, the second hole transportinglayer 224 is formed in the red and green pixel areas Rp and Gp. Also, inthe red pixel area RP, the red organic light-emitting pattern 242, thegreen organic light-emitting pattern 244, and the blue organiclight-emitting pattern 246 are stacked to form the first emittingmaterial pattern 247 with the three-layered structure, in the greenpixel area Gp, the green organic light-emitting pattern 244 and the blueorganic light-emitting pattern 246 are stacked to form the secondemitting material pattern 248 with the two-layered structure, and in theblue pixel area Bp, the blue organic light-emitting pattern 246 formsthe third emitting material pattern 249 with the signal layer.Accordingly, the second emitting material pattern 248 is thinner thanthe first emitting material pattern 247 and thicker than the thirdemitting material pattern 249.

Meanwhile, the capping layer 270 is used to enhance a light extractioneffect, and may be formed of one among materials for forming the firstand second hole transporting layers 222 and 224, materials for formingthe electron transporting layer 250, and host materials for forming thered, green, and blue organic light-emitting patterns 242, 244, and 246.However, the capping layer 270 may be omitted.

The organic light-emitting diode according to the second embodiment, asdescribed above, requires no additional mask process although it has amicrocavity structure.

Referring again to FIG. 4, after the anode 210 is formed, the holeinjection layer 220 and the first hole transporting layer 222 are formedusing a first fine metal mask. The hole injection layer 220 is formed bydoping a material for forming the first hole transporting layer 222 witha p-type dopant, for example, boron, and the hole injection layer 220and the first hole transporting layer 222 may be formed using the firstfine metal mask in a first chamber.

Then, in a second chamber, the second hole transporting layer 224 isformed in the red and green pixel areas Rp and Gp using a second finemetal mask.

Successively, in a third chamber, the electron blocking layer 230 isformed using a third fine metal mask in the red, green, and blue pixelareas Rp, Gp, and Bp.

Then, in a fourth chamber, the red organic light-emitting pattern 242 isformed in the red pixel area Rp using a fourth fine metal mask, and in afifth chamber, the green organic light-emitting pattern 244 is formed inthe red and green pixel areas Rp and Gp using a fifth fine metal mask.Thereafter, in a sixth chamber, the blue organic light-emitting pattern246 is formed in the red, green, and blue pixel areas Rp, Gp, and Bpusing a sixth fine metal mask.

Thereafter, in seventh, eighth, and ninth chambers, the electrontransporting layer 250, the cathode 260, and the capping layer 270 aresequentially formed.

That is, since processes are performed using 9 fine metal masks in atotal of 9 chambers, a microcavity structure may be implemented withoutcausing an increase of a fabrication cost and complexity of afabrication method.

Since the second hole transporting layer 224 is formed in the red andgreen pixel areas Rp and Gp, the second embodiment may reduce the numberof processes compared to the first embodiment in which both the secondand third hole transporting layers 124 and 126 are formed. Meanwhile, byforming the first emitting material pattern 247 having the three-layeredstructure in the red pixel area Rp and the second emitting materialpattern 248 having the two-layered structure in the green pixel area Gpalthough the third hole transporting layer 126 of the first embodimentis omitted, it is possible to maintain the differences in cavitythickness in the pixel areas Rp, Gp, and Bp.

The emission property of the emitting material pattern structure asdescribed above depends on the order in which emitting material patternsare stacked.

Referring to FIG. 5A showing an emission spectrum when a green organiclight-emitting pattern and a blue organic light-emitting pattern aresequentially stacked on a red organic light-emitting pattern (RedEML/Green EML/Blue EML), although the green and blue organiclight-emitting patterns are stacked on a red organic light-emittingpattern, a red emission spectrum is displayed.

However, referring to FIG. 6A showing an emission spectrum when a redorganic light-emitting pattern is stacked on a blue organiclight-emitting pattern (Blue EML/Red EML), both blue and red emissionspectrums are displayed.

That is, in the second embodiment having the lamination structure of thered, green, and blue organic light-emitting patterns 242, 244, and 246,the color properties may be maintained, however, different structuresdeteriorate color properties.

Also, referring to FIG. 5B showing an emission spectrum when a blueorganic light-emitting pattern is stacked on a green organiclight-emitting pattern (Green EML/Blue EML), although the blue organiclight-emitting pattern is formed on the green organic light-emittingpattern, a green emission spectrum is displayed.

However, referring to FIG. 6B showing an emission spectrum when a greenorganic light-emitting pattern is stacked on a blue organiclight-emitting pattern (Blue EML/Green EML), both blue and greenemission spectrums are displayed.

That is, in the second embodiment having the lamination structure of thegreen and blue organic light-emitting patterns 244 and 246, the colorproperties may be maintained, however, different structures deterioratecolor properties.

Emission in an organic light-emitting layer mainly occurs between theorganic light-emitting layer and an electron blocking layer. If there isno electron blocking layer, emission will occur at the interface betweenthe organic light-emitting layer and a hole transporting layer.

Accordingly, for example, in the case of the red pixel area Rp of theorganic light-emitting diode shown in FIG. 4, emission mainly occurs atthe interface between the red organic light-emitting pattern 242 and theelectron blocking layer 230.

Also, the energy bandgap of the green organic light-emitting pattern 244is greater than the energy bandgap of the red organic light-emittingpattern 242 and smaller than the energy bandgap of the blue organiclight-emitting pattern 246. Electrons and holes that have been coupledand emitted light in an organic light-emitting pattern having an energybandgap can again emit light in an organic light-emitting pattern havingthe narrower energy bandgap. However, electrons and holes that have beencoupled and emitted light in an organic light-emitting pattern having anenergy bandgap cannot emit light in an organic light-emitting patternhaving the wider energy bandgap.

Accordingly, in a structure in which a blue organic light-emittingpattern and a green or red organic light-emitting pattern aresequentially stacked between an anode and a cathode, electrons and holesthat have been coupled and emitted light in the blue organiclight-emitting pattern can again emit light in the green or red organiclight-emitting pattern. However, in a structure in which red, green, andblue organic light-emitting patterns are sequentially stacked between ananode and a cathode, electrons and holes that have been coupled andemitted light in the red organic light-emitting pattern do not emitlight in the green and blue organic light-emitting patterns. Also, in astructure in which green and blue organic light-emitting patterns aresequentially stacked between an anode and a cathode, electrons and holesthat have been coupled and emitted light in the green organiclight-emitting pattern do not emit light in the blue organiclight-emitting pattern having a wider energy bandgap.

Accordingly, in the structure as shown in FIG. 4 in which the red,green, and blue organic light-emitting patterns 242, 244, and 246 arestacked in the red pixel area Rp, as shown in FIG. 5A, only a redemission spectrum is displayed, while in the structure in which the blueand red organic light-emitting patterns are stacked, as shown in FIG.6A, both blue and red emission spectrums are displayed.

Also, in the structure as shown in FIG. 4 in which the green and blueorganic light-emitting patterns 244 and 246 are stacked on the greenpixel area Gp, as shown in FIG. 5B, only a green emission spectrum isdisplayed, while in the structure in which the blue and green organiclight-emitting patterns are stacked, as shown in FIG. 6B, both blue andgreen emission spectrums are displayed.

That is, only the lamination structure of red, green, and blue pixelareas Rp, Gp, and Bp, as shown in FIG. 4, can represent desired colors.

As described above, the organic light-emitting diode can improve lightoutput efficiency using a microcavity structure.

Also, it is possible to implement the microcavity structure withoutincreasing the number of processes and to prevent a fabrication costfrom increasing and a fabrication method from being complicated.

In addition, it is possible to maintain color properties and displayhigh-quality images even when different organic light-emitting patternsare stacked in red and green pixel areas for the microcavity structure.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in a display device of thepresent disclosure without departing from the sprit or scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

What is claimed is:
 1. An organic light-emitting diode comprising: asubstrate on which a red pixel area, a green pixel area, and a bluepixel area are defined; an anode disposed on the substrate andcorresponding to the red pixel area, the green pixel area, and the bluepixel area; a first hole transporting layer disposed on the anode andcorresponding to the red pixel area, the green pixel area, and the bluepixel area; a second hole transporting layer disposed on the first holetransporting layer and corresponding to the red pixel area and the greenpixel area, the second hole transporting layer having a uniformthickness; a first emitting material pattern disposed on the second holetransporting layer and corresponding to the red pixel area, the firstemitting material pattern having a first thickness; a second emittingmaterial pattern disposed on the second hole transporting layer andcorresponding to the green pixel area, the second emitting materialpattern having a second thickness; a third emitting material patterndisposed on the first hole transporting layer and corresponding to theblue pixel area, the third emitting material pattern having a thirdthickness; an electron transporting layer disposed on the first emittingmaterial pattern, the second emitting material pattern, and the thirdemitting material pattern and corresponding to the red pixel area, thegreen pixel area, and the blue pixel area; and a cathode disposed on theelectron transporting layer and corresponding to the red pixel area, thegreen pixel area, and the blue pixel area, wherein the second thicknessis less than the first thickness and greate than the third thickness. 2.The organic light-emitting diode according to claim 1, wherein the firstemitting material pattern has a three-layered structure in which a redorganic light-emitting pattern, a green organic light-emitting pattern,and a blue organic light-emitting pattern are stacked on the second holetransporting layer.
 3. The organic light-emitting diode according toclaim 2, wherein the second emitting material pattern has a two-layeredstructure in which the green organic light-emitting pattern and the blueorganic light-emitting pattern are stacked on the second holetransporting layer.
 4. The organic light-emitting diode according toclaim 3, wherein the third emitting material pattern has a single layerstructure consisting of the blue organic light-emitting pattern.
 5. Theorganic light-emitting diode according to claim 1, wherein the anode isa reflective electrode, the cathode has a semi-transparent property andis spaced first, second, and third distances apart from the anode in thered pixel area, the green pixel area, and the blue pixel area,respectively, and the second distance is shorter than the first distanceand longer than the third distance.
 6. The organic light-emitting diodeaccording to claim 1, wherein an electron injection layer is interposedbetween the first electron transporting layer and the anode, and theelectron injection layer is formed by doping a material for forming thefirst electron transporting layer with a p-type dopant.
 7. The organiclight-emitting diode according to claim 1, wherein an electron blockinglayer is formed between the second hole transporting layer and each ofthe first and second emitting material patterns, and between the thirdemitting material pattern and the first hole transporting layer.
 8. Amethod of fabricating an organic light-emitting diode, comprising:forming an anode on the entire surface of a substrate on which a redpixel area, a green pixel area, and a blue pixel area are defined;forming a first hole transporting layer on the anode and correspondingto the red pixel area, the green pixel area, and the blue pixel area;forming a second hole transporting layer on the first hole transportinglayer and corresponding to the red pixel area and the green pixel area,the second hole transporting layer having a uniform thickness; forming ared organic light-emitting pattern on the second hole transporting layerand corresponding to the red pixel area; forming a green organiclight-emitting pattern on the red organic light-emitting pattern and thesecond hole transporting layer; forming a blue organic light-emittingpattern on the green organic light-emitting pattern and the first holetransporting layer; forming an electron transporting layer on the blueorganic light-emitting pattern; and forming a cathode on the electrontransporting layer.
 9. The method according to claim 8, before formingthe first hole transporting layer, further comprising forming a holeinjection layer on the anode, wherein the hole injection layer is formedby doping a material for forming the first hole transporting layer witha p-type dopant, and the hole injection layer and the first holetransporting layer are formed in the same chamber.